Hydrofoil craft



April 1968 J. F. LSTIBUREK 3,380,421

HYDROFOIL CRAFT Filed July 11. 1966 2 Sheets-Sheet 1 I NVEN'TOR. JOSEFF. LS TIBURE K Aqent April 30, 1968 J. F. LSTIBUREK HYDROFOIL CRAFT 2Sheets-Sheet t.

A B NEED H 52mm Filed July 11, 1966 JOSEF F LSTIBUREK United StatesPatent M 3,380,421 HYDROFOIL CRAFT Josef F. Lstiburek, 157 Richard ClarkDrive,

Downsview, Ontario, Canada Filed July 11, 1966, Ser. No. 564,318 4Claims. (Cl. 11466.5)

ABSTRACT OF THE DISCLOSURE A small watercraft hydrofoil system includinga fixed incidence hydrofoil means positioned at a single longitudinalstation on the craft bull in a position substantially beneath the centreof gravity of the loaded craft and such that when the craft isfoil-borne, the weight of the craft is fully supported by the singlehydrofoil means and the centre of pressure of the hydrofoil means iscoincident with or slightly aft of the centre of gravity of the craft. Avariable incidence stabilizer plate means extending beneath the craftaft of the hydrofoil means and adjustable in horizontal angle relativeto the longitudinal axis of the craft permits the attitude of the craftand the angle of attack of the hydrofoil means to be readily controlled.The hydrofoil means and the variable incidence plate means are adaptedfor retraction upwardly, thus facilitating land transportation,launching and beaching of the craft.

This invention relates to a hydrofoil system for use with a boat, and inparticular it is directed to a small watercraft embodying the hydrofoilsystem.

Hydrofoil systems for use with boats for over the water propulsion arewell known. A hydrofoil, comprising an arrangement of hydrodynamicallyshaped foil sections depending downwardly in supporting relation withthe hull of a vessel, provides lift to the vessel to raise the vesselhull clear of the water surface upon the attainment of a suificientforward speed, thereby ridding the vessel of the parasitic hull drag ofthe water which, in conventional craft, presents an obstacle to theachievement of higher speeds.

A major problem encountered by prior hydrofoil arrangements has been theachievement of longitudinal stability of the vessel. This problem arisesowing to the fact that variation in the longitudinal attitude of thevessel relative to its direction of motion changes the effective angleof attack of the hydrofoil elements, thereby varying the effective liftof the elements, so causing an unstable condition which can result inviolent raising and lowering of the hydrofoil members and hulltherewith, together with a violent porpoising effect if an unstablecondition is reached.

In the main, prior arrangements have been characterized by amultiplicity of hydrofoil members arranged at different positions alongthe length of the vessel with each providing a part of the lifting forcerequired to raise the hull above the water surface in operation. Many ofthe prior systems incorporate a sensing device to provide automaticvariations in the angle of attack of at least one hydrofoil member in aneffort to provide automatic stabilizing of the vessel in its progressover rough water.

Although a number of generally satisfactory hydrofoil systems have beendeveloped for large, relatively high length-to-beam ratio watercraft,none of the prior art systems has been successfully adapted for use withsmall pleasure craft of relatively low length-to-beam ratio. The presentinvention provides such a craft. In accordance with the invention, afixed incidence hydrofoil means is located at a single longitudinalstation on the vessel in a position substantially beneath the centre ofgravity of 3,380,421 Patented Apr. 30, 1968 the loaded craft and suchthat when the craft is foilborne, the weight of the craft is fullysupported by the single hydrofoil means and the centre of pressure ofthe hydrofoil means is coincident with or slightly aft of the centre ofgravity of the craft. A variable incidence stabilizer plate meansextending beneath the vessel aft of the hydrofoil means and adjustablein horizontal angle relative to the longitudinal axis of the vesselpermits the attitude of the vessel and the angle of attack of thehydrofoil means to be readily controlled. During foil-borne operations,the stabilizer plate means does not function to provide lift at thestern. In functions to provide either an essentially neutral stabilizingeffect when the centre of pressure of the hydrofoil is coincident withthe centre of gravity; or, when the centre of pressure of the hydrofoilmeans is aft of the centre of gravity of the craft, the plate provides adownward force to compensate for the lifting moment at the stern. Thisarrangement has been found to provide exceptional longitudinal stabilityof the craft in operation.

Transverse stability of the arrangement is provided by the use of a pairof V-form hydrofoils. Each of the hydrofoil pair includes subsidiarybarrier fins extending normally inwardly at a point slightly above theapex of the V of the foil to minimize the entrainment of air along thesurface of the foil. Also, a downwardly extending keel means located atthe apex of each of the foil pair provides lateral resistance againstsideways skidding of the craft during turns.

The stern of the craft is recessed forwardly to receive an outboardmotor suspended in propulsive arrangement from a transverse transomportion of the recessed well. The variable incidence plate means extendsrearwardly from the stern, preferably being positioned substantially inline with the axis of the propeller of the motor in order to increaseits defiective effectiveness, particularly at lower speeds.

In order to facilitate handling of the vessel, the hydrofoil and thevariable incidence plate, together with the propulsive motor are adaptedfor retraction upwardly, thus facilitating land transportation,launching and beaching of the vessel.

While the preferred embodiment is for relatively low length-to-beamratio personal run-abouts holding up to six passengers, it iscontemplated that larger versions of the arrangement may be utilized.

Broadly, the water borne hydrofoil craft of the invention comprises ahull portion for floating on water adapted to receive fluid reactionmeans in attached propulsive relation therewith; hydrofoil meansattached to the craft and adapted to fully support the hull above thewater at speed, the longitudinal position of said hydrofoil means beingselected such that the centre of pressure thereof when the hull isfoil-borne coincides with or is aft of the centre of gravity of theloaded craft; variable incidence stabilizer plate means extensible belowthe hull of the craft, located longitudinally from the hydrofoil meansto control the angle of incidence of the craft together with the angleof attack of the hydrofoil means, and control means for selectivelyvarying the angle of incidence of the plate means to provide a neutralor negative lift at the stern when the craft is foil-borne.

Certain embodiments of the present invention are described by way ofexample, reference being bad to the accompanying drawings wherein:

FIGURE 1 is a general perspective view of the craft in the operativecondition;

FIGURE 2 is a perspective view showing the underside of the craft;

FIGURE 3 is a partial perspective view showing details of the stabilizerplate mounting and control means;

FIGURE 4 is a partly sectional detail of the incidence control of thevariable plate means; and

FIGURE 5 is a schematic illustration showing the relative positioning ofthe centre of gravity of the craft and the centre of pressure of thehydrofoil in foil-borne operation.

Referring first to FIGURES l, 2. and 3, the hydrofoil craft includes astreamlined hull formed of glass fibre, reinforced plastic or the likeand having a pair of hydrofoil assemblies 21, 22 attached thereto. Eachassembly 21, 22 is of V-form and comprises an inner foil member 23 andan outer foil member 24. Foil members 24 are pivotally attached to theunderside of hull 25 at their inner ends by means of pivotal mountings26 fixed to the bottom of hull 25 adjacent the centre line thereof. Theouter foil members 24, in fixed angular relation with the inner foilmembers 23, are secured to the hull 25 by support arms 27, attached byfoil pivot brackets 28 and brace frames 29 arranged in triangulated,braced relation therewith.

As shown particularly in FIGURE 3, the hull 25 of the craft is formedwith a stern well including vertical sidewalls 36 and a lateral transom39 at the forward end thereof adapted to permit rigid attachment of anoutboard motor or propulsive means (not shown) thereto. It is alsocontemplated that the present invention may be adapted for use with anaircraft type propeller drive upon suitable adjustment of the relativelongitudinal position of the hydrofoil means to compensate for thechanged ccccntricity of thrust.

The rear stabilizer assembly d5 comprises a substantially flatstabilizer plate 46 having leading and trailing sharp edges. The plate46 is mounted on pivot pins 47 secured to a pair of support brackets 43,48a. A control bracket 49 extends upwardly from the plate 46 and isconnected to a control rod 50 by means of a clevis end 51 and a pin 52extending through the clevis end 51 and rod 50.

The stabilizer assembly 45 is secured to the hull 25 of the craft bymeans of a pair of tubular suspension struts 56, 56a to which thesupport brackets 48, 48a are secured. Struts 56, 56a each have astiffening member 57 secured to the underside thereof and pivotallymounted on stern well sidewalls 36 by pivot mountings 58.

Each of the stabilizer support struts 5s, 56:: has a holding plate 60secured to the upper end thereof adapted to releasably engage a strutsecuring pin 51 attached to each side 36 of stem well 35 by a bracket62. A strut retracting bar 63 is pivotally connected to plate 68 bytransverse pin 64 and has a hole 65 formed therethrough at a pointintermediate pin 64 and its free end, which is provided with hand gripon to facilitate manual manipulation thereof. It will be seen that thearrangement just described enables the stabilizer assembly 45 to besecured in a fixed, operative position as shown in FIGURES 1-3 or to bemoved and secured in a retracted position by raising bars 63,disengaging plates 66 from pins 61, pushing the inner ends of struts 56,56a downward and engaging holes 65 in bars 63 with pins 61.

Referring particularly to FIGURE 4, the means for controlling the angleof incidence of the variable plate 46 relative to the horizontalcomprises a rotatable shaft 71 mounted in a thrust plug '72 within theupper end of the stabilizer support arm 56:: by means of a pair oftransverse pins 73 which engage a groove 74 in shaft 71. The inner endof the shaft 71 has a threaded portion 75 in threaded engagement with athreaded recess 76 of the control rod 50. As shown in FIGURE 3, astabilizer control handle 77 conveniently positioned near the operatorsposition in the craft cockpit is connected to shaft 71 by torque tube 78and flexible coupler 7%. Rotation of the shaft 71 by means of controlhandle 77 produces an extension or shortening of the control rod 50,thus enabling precise control of the angle of plate 46 from the cockpit.Rotation of the rod 50 is prevented by virtue of the clevis joint 51 atthe outer end thereof engaging the control bracket 4-9.

Referring now to the details of the hydrofoil pivotal mountingarrangement illustrated in FIGURES 1, 2 and 3, the brace frames 29include a first bracing strut 80 pivotally connected to support arms 27adjacent the outer ends thereof by support arm pivot brackets 81 andpivotally secured to the side of hull 25 by forward hull brackets 32. Asecond bracing strut 83 is fixed such as by welding to each first strut80 at its outer end and is pivotally secured to hull 25 by aft hullbrackets 84. The inner ends of the support arms 27 are detachably,pivotally secured to boat hull 25 at a first outboard position indicatedby the numeral 85 (the position of the left arm 27 in FIG- URE 3) andmay be resecured to a position adjacent the centre line of the boat atthe top of the hull to a holding bracket 86 to secure foil assemblies21, 22 in a retracted position (the position of the right-hand arm inFIGURE 3).

An important feature of the hydrofoil boat arrangement of this inventionis the location of the hydrofoil assemblies 21, 22 at a longitudinalposition on the boat hull substantially beneath the centre of gravitysuch that the weight of the boat is fully supported by the hydrofoilmeans 21, 22 when the craft is foil-borne. That is, the positioning ofthe foil means 21, 22 must be such that when the loaded craft is infoil-borne operation, the centre of pressure of foils is coincident withor slightly aft of the centre of gravity of the craft. The stabilizerassembly 45 does not function as a hydrofoil element. In normaloperation it exerts either a neutral or a negative lifting force at thestern of the craft. Any negative force must be sufiicient only tocompensate for the lifting moment at the stern resulting from thepositioning of the hydrofoil means such that the centre of pressure isaft of the centre of gravity of the craft as shown schematically inFIGURE 5. Preferably, the centre of pressure is coincident with thecentre of gravity or aft thereof a distance less than 10% of the hulllength. This arrangement provides excellent longitudinal stability inthe foil-borne operation of the craft. Also, by selecting a hullconfiguration in which the variation of the centre of gravity of thecraft due to passenger movement is substantially controlled in thelongitudinal sense by the utilization of a single transverse seatarrangement, a particularly stable and readily controlled vessel isprovided.

Also, in the matter of stability, the provision of a downwardlyextending keel portion 90 at the apex of the foil members 23, 24prevents undue sideways skidding motion of the craft during high speedturns, while anti-ventilation barriers 91 comprising plate portionsextending normally from each of the foil members 23, 24 at a point abovethe apexes prevent the access of air along the top surface of the foilin the low pressure lift region so that cavitational flow is avoided andseparation which may occur with the presence of air bubbles at thispoint, is substantially eliminated.

A particular advantage afforded by the present arrangement asillustrated is the arrangement of the stabilizer plate 46 below thebottom of the craft and behind the propulsive means which ensureseffective stabilizing operation of the plate 46 even at relatively lowspeeds, owing to the motion of water therepast due to the action of thepropeller.

It will be understood that the vessel can be operated in a relativelyunrestricted fashion as an orthodox boat when the foils 21, 22 andstabilizer, assembly 45 respectively are retracted. Retraction of thestabilizer plate 46 need not be effected for hydrodynamic reasons but iscarried out principally to facilitate operation in shallow waters withthe hull in the immersed position for carrying out operations such asbeaching and launching.

It is to be understood that the form of the invention herein shown anddescribed is to be taken as a preferred example of the same and thatvarious changes in the shape, size and arrangement of the parts may beresorted to without departing from the spirit of the invention or thescope of the appended claims.

What I claim as new and desire to protect by Letters Patent of theUnited States is:

1. A water borne hydrofoil craft comprising: a hull portion for floatingon water adapted to receive fluid reaction means in attached propulsivearrangement therewith; hydrofoil means attached to the craft adapted tosupport the full weight of the craft above water at operational speeds,said hydrofoil means being located at a longitudinal position such thatin foil-borne operation, the centre of pressure of the hydrofoil meansis between the centre of gravity of the loaded craft and a pointslightly aft of said centre of gravity; said hydrofoil means comprisinga pair of independent V-shaped groups of foils suspended side-by-sidefrom said hull portion with each pivotally connected at the inner endthereof to the bottom of the craft, a pair of support arms'pivotallyconnected with the outer ends of said foils extending inwardly anddetacha'bly pivotally secured to the upper outboard edge of the hull,bracing struts pivotally attached to said support arms adjacent theirouter ends extending inwardly in a triangulated arrangement andpivotally attached to the side of the hull, said foils, support arms andbracing struts adapted for upward retractive movement; variableincidence plate means extensible below the hull of the craft, locatedlongitudinally from said hydrofoil means to control the angle ofincidence of the craft together with the angle of attack of thehydrofoil means, and control means for selectively varying the angle ofincidence of the said plate means.

2. A hydrofoil craft as claimed in claim 1 wherein said variableincidence plate means comprises a substantially flat rigid plate withsharp loading and trailing edges and connected by pivot mounting meansto a support structure extending downwardly and rearwardly from saidhull.

3. A- hydrofoil craft as claimed in claim 2 wherein said variableincidence plate means is operatively connected with a control meansextending from the craft cockpit whereby the angle of incidence of saidplate means can be varied by the operation when the craft is in motion.

4. A water borne hydrofoil craft comprising: a hull portion for floatingon water adapted to receive fluid reaction means in attached propulsivearrangement therewith; hydrofoil means attached to the craft adapted tosupport the full weight of the craft above the water at operationalspeeds, said hydrofoil means being located at a longitudinal positionsuch that in foil-borne operation, the centre of pressure of thehydrofoil means is between the centre of gravity of the loaded craft anda point slightlyaft of said centre of gravity; variable incidence platemeans extensible below the hull of the craft, located longitudinallyfrom said hydrofoil means to control the angle of incidence of the crafttogether with the angle of attack of the hydrofoil means, and controlmeans for selectively varying the angle of incidence of said plate meansincluding an upright bracket fixed at one side of the plate means, anon-rotatable control rod pivotally connected to said bracket andextending forwardly towards the craft cockpit, a rotatable torque memberextending rearwardly from the craft cockpit, means "connecting saidtorque member and control rod such that rotational movement of thetorque member effects controlled reciprocatory movement of said controlrod.

References Cited UNITED STATES PATENTS 2,914,014 11/1959 Carl et al114-665 2,991,747 7/1961 Bader et al. 114-665 3,104,642 9/1963 Piazza11466.5

FOREIGN PATENTS 715,558 9/1931 France.

OTHER REFERENCES A.P.C. application of O. Tietjens, Ser. No. 268,421,published May 11, 1943.

ANDREW H. FARRELL, Primary Examiner.

